Polyphosphazenes are polymers containing a plurality of --P&lt;.dbd.N-- units wherein substituents are bonded to the phosphorus atoms. The properties of the polymer are largely governed by the nature of the phosphorus substituents. These substituents can vary widely and include among others, aryloxy, alkaryloxy, arylalkoxy, alkoxy, aminoaryloxy, nitroaryloxy, alkenoxy, alkenylaryloxy, halo, amino, alkylamino, dialkylamino, aryl, alkaryl, alkyl, aralkyl and the like including all combinations thereof. The polyphosphazenes which are the concern of the present invention are high molecular weight substantially linear polyphosphazenes which contain from about 100 up to 1,000,000 or more of the above units.
Polyphosphazenes which are substituted with phenoxy, alkylphenoxy and large amounts of alkoxy are known. Reynard et al., U.S. Pat. No. 3,856,712 describes such polymers in which 40-80 mole percent of the phosphorus substituents are alkoxy. Although such polymers have low glass transition temperatures (Tg), it has been found that they are relatively high smoke generators in standard smoke tests. Since one of the most important uses of polyphosphazene compositions is in applications where smoke generation during fires can be hazardous, a need exist for a polyphosphazene with low-smoke properties which still exhibit an acceptably low Tg.